In situ TEM study of crack–grain boundary interactions in thin copper foils

  In situ tensile experiments were performed in a transmission electron microscope to investigate the interaction of an advancing crack with grain boundaries in thin copper foils. Cracks propagate within the grains on slip planes due to plastic flow, thinning and overload. Certain grain boundaries are effective in arresting the crack whereas others are not. The stress field of the arrested crack then activates multiple deformation modes in the grain ahead of the crack tip. The observations have significant implications for grain boundary engineering in polycrystalline metal films.